1. Field of the Invention
This invention concerns the collection of liquids to be filtered in a filtration system from a number of different locations.
2. Description of the Prior Art
Industrial filtration equipment is often employed to filter coolants directed at the cutting tools during the machining process. The coolant, metal chips, and other debris generated are collected in a sump and are circulated to the filtration equipment. This coolant flow has in the past been accomplished by flow in so-called velocity trenches, which are below grade concrete, steel lined channels which direct the dirty coolant liquid, chips, and debris back to the filtration equipment.
In recent years, below grade concrete, steel lined trenches have become disfavored since undetected leaks may occur, sometimes causing considerable contamination of the soil beneath the plant.
Copending U.S. application Ser. No. 08/131,298 filed on Oct. 8, 1993 now U.S. Pat. No. 5,380,446, by the present inventor describes a vacuum collection system using in-line filter units. This approach requires pressurized filters, which are not currently in widespread use in this field. Rather, open-topped tank filters are typically employed.
Above grade piping networks have also been used, in which a pump is associated with each sump, pumping the collected liquid back to a conventional filtration equipment via overhead pipes.
There are several disadvantages to this latter approach.
Firstly, having an industrial pump at each sump requires the wiring of each pump and starter with 440 volt lines. There are typically a large number of sumps involved with a typical installation, and thus involving substantial costs, particularly if a spare pump is specified for each sump so that the system need never be shut down for maintenance.
The extra pump at each sump increases the size of the sump, and also makes it impractical to collect liquid beneath each wing base in a transfer line as the pumps cannot be fit beneath the base.
The individual relatively small capacity pumps are not as durable as large capacity industrial pumps, creating a maintenance burden, particularly since these small capacity pumps, with their relatively tight clearances tend to become clogged with the machining chips.